Omega-3 fatty acids induce macrophage IL-22 signaling to promote resolution of dust-induced lung inflammation

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PROJECT SUMMARY Inhalation of aerosolized dusts from urban, rural, and farming environments can trigger harmful airway inflammation and injury; over time, continual exposure to these particulates increases one's risk for developing inflammatory airway diseases. While dust exposures negatively impact lung health, factors contributing to protection versus susceptibility to lung disease following these continual inhalational exposures are unclear. A recently discovered class of specialized pro-resolving lipid mediators (SPM) derived from omega-3 fatty acids regulate lung inflammation, immunity, and repair, and are likely key to the beneficial effects of diets high in omega-3 fatty acids. Our previous investigations identified that the omega-3 fatty acid docosahexaenoic acid (DHA) and its lipid metabolite maresin-1 (MaR1) mitigate airway inflammation from acute and repetitive organic dust exposure, mediated in part by macrophage activation and pro-repair activities on the airway epithelium. Our exciting new data identify that omega-3 fatty acids and MaR1 can activate IL-22 signaling in lung macrophages. IL-22 signaling promotes mucosal immunity and epithelial barrier integrity, and its activation in the presence of these bioactive lipids may be key to their protective effects. Furthermore, our novel finding of IL-22 signaling in macrophages challenges current dogma regarding the activation and regulation of this pathway. The goal of this proposal is to investigate the role of omega-3 fatty acids in promoting pro-repair IL-22 signaling in the lung following dust exposures. We hypothesize that omega-3 fatty acids and SPM promote lung recovery following particulate matter exposures by inducing alveolar macrophage IL-22 production that subsequently promotes alveolar macrophage pro-resolution polarization and lung epithelial repair. To test this hypothesis, in Aim 1, we will establish the impact of omega-3 fatty acids and IL-22 on lung recovery following dust exposure. In Aim 2, we will evaluate the role of omega-3 fatty acids and IL-22 in epithelial repair and mucosal immunity during dust exposure. In Aim 3, we will identify how SPM and IL-22 signaling impacts lung macrophage polarization. Together, our studies will identify how omega-3 fatty acids modulate susceptibility versus resilience to dust exposures, including a novel protective mechanism via activation of macrophage IL- 22 signaling to promote tissue repair and mucosal immunity. We expect our studies' findings to guide novel treatment strategies for lung disease.